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Mahmod Issa
11,745 PointsWhy cast Button if it is already a type view of Button?
In the textView i should cast the variable because it is not a view type, so why should I cast Button if it is already button?
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class FunFactsActivity extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fun_facts);
// Declare our View variables and assign them the Views from the layout file
TextView factLabel = (TextView) findViewById(R.id.factTextView);
Button showFactButton;
}
}
1 Answer
Jacob Bergdahl
29,119 PointsButton and TextView are both children of View. The findViewById() method returns a View. So, if you say something like Button button = findViewById(), it won't work, since a View isn't necessarily a Button (although a Button is always a View). For this reason, you have to cast it.
Mahmod Issa
11,745 PointsMahmod Issa
11,745 PointsYou mean that Button and TextView are subclasses of View?
Jacob Bergdahl
29,119 PointsJacob Bergdahl
29,119 PointsCorrect! In fact, all widgets, not only Buttons and TextViews, are children of the base class View. ViewGroup is also a subclass of View, and is used for Views that contain other Views, such as LinearLayout and RelativeLayout.